1. Field of the Invention
The present invention relates generally to radiation cross-linked polyurethane foams, to a foam-forming composition useful in the preparation of said foams, and to a process for preparing said foams. More particularly, the present invention relates to a foam-forming composition comprising
(a) a polyol selected from the group consisting of polyester polyols, polyether polyols having a molecular weight of about 1500 or less, and mixture of a polyester polyol and a polyether polyol wherein the polyester polyol has a molecular weight of from about 400 to about 5000 and the polyether polyol has a molecular weight of from about 250 to about 6500,
(b) an organic polyisocyanate, and
(c) a cross-link promoter selected from the group consisting of polyfunctional, polyunsaturated acrylates; polyfunctional, polyunsaturated methacrylates; triallyl cyanurate; methyl methacrylate; 1,5-cyclooctadiene and bis (.beta.-chloroethyl) vinyl phosphonate.
Foams prepared from the above formulations are subjected to a suitable radiation source at a dosage and for a time sufficient to modify the properties of the foam. In this manner, foams having improved properties, such as increased tensile strength, tear strength and percent compression-deflection can be produced.
2. Description of the Prior Art
Foamed polyurethane materials derived from the reaction product of an organic polyisocyanate and an active-hydrogen containing compound such as polyols, including polyethers, polyesters, polyoxycarboxy alkylenes, and the like are well-known in the art. However, for certain applications it would be desirable to have a foam with properties different than those exhibited by conventional polyurethane foams. These desirable properties include improved dimensional stability both at ambient and at elevated temperatures, improved toughness, increased solvent resistance, greater resistance to creep, more permanent flame-proofness and greater impact resistance.
The crosslinking of polymeric materials by exposure to high intensity radiation and the use of a variety of materials as cross-link promoters have previously been disclosed. However, it has not heretofore been suggested that radiation cross-linked polyurethane foams could be prepared by the use of a specific group of crosslink promoters or that such foams would have modified properties.